Low-pressure arc-discharge tube arrangement



June 4, 1957 J. c. MOERKENS 2,794,938

Low-PRESSURE ARC-DISCHARGE TUBE ARRANGEMENT Filed March 3, 1954 INVE NTOR JOZEF CORNELIS MOERKENS LOW-PRESSURE ARC-DISCHARGE TUBE ARRANGE JozefCornelis Moerkens, Eindhoven, Netherlands, assignor, by mesneassignments, to North American Philips Company, Inc., New York, N. Y., acorporation of Delaware Application March 3, 1954, Serial No. 413,881Claims priority, application Netherlands March 5, 1953 3 Claims. (Cl.315-138) The present invention relates to a low pressure arc-dischargetube arrangement. More particularly, the invention relates to anarrangement without a starting switch for operating two low-pressurearc-discharge tubes, es-

pecially, but not exclusively, fluorescent lamps. Each comprises twoactivated main electrodes and at least one auxiliary electrode which isdisposed within the discharge space on the wall of the discharge vessel,and is connected electrically within the discharge space to one of themain electrodes and is electrically insulated from the other mainelectrode and extending parallel to the discharge path. Each tube has,in addition, a rare gas filling at a pressure of a few mm. According tothe invention, one tube is arranged for connection to an A. C. supply ofthe arrangement in series with a first inductance, the other tube beingarranged for connection to said supply in series with a secondinductance and with a capacitor, whose impedance exceeds that of thesecond inductance, and in series with part of the first inductance, inwhich arrangement the series-combination of the tube connected in serieswith the capacitor, of the second inductance and of said part of thefirst inductance is shunted by an auxiliary inductance.

, ited States Patent choke part 6, while the part 9293 is connected inseries As a result of this arrangement the two tubes ignite at V avoltage exceeding the supply voltage, to the effect of attaining thearc-discharge condition very rapidly, whereby the number of times thetube can be brought into circuit is greatly increased.

Difficulties may, however, be experienced if one of the tubes becomesdefective.

If, for example, the tube connected in series with the capacitor (thatis to say the capacitatively stabilized tube) fails, only the supplyvoltage is available for igniting the other (inductively stabilized)tube, since the voltageincreasing influence of the capacitative tubebranch is lacking. Due to this, the inductively stabilized tube willeither not ignite or it will attain the arc-discharge condition in anundesirably slow manner and take a current smaller than the normaloperating current.

If, in contradistinction thereto, the inductively stabilized tube isdefective, the capacitatively stabilized tube will take a currentexceeding the normal operating current.

According to another feature of the invention, said disadvantages aresubstantially eliminated if the auxiliary inductance constitutes thevoltage-increasing secondary winding of a transformer, the primarywinding of which is connected, in series with the capacitor, to thecurrent supply of the arrangement.

At a supply voltage of approximately 220 volts it is advantageous forthe number of primary turns of said transformer to be 82 to 95% of thatof the secondary turns. In this case, the number of turns of the firstinductance, connected in the two tube circuits, is 20 to 30% of thetotal number of turns of the first inductance.

In order that the invention may be readily carried into effect, it willnow be described in greater detail with reference to the accompanyingdrawing, in which the single Patented June 4, 1957 ice rescent layer(not shown) comprise two main electrodes 11, 12 or 21, 22, which areactivated by barium-strontium compounds, and an auxiliary electrode 13or 23. The

auxiliary electrodes consist of a mixture of graphite and glaze and areapplied to the inner surface of the tube wall in the form of a stripapproximately 3 mins. wide running substantially the whole length of thetube. The strips are each connected to one of themain electrodes andhave a resistance of approximately 20 to 30 ohms per cm. If desired,each tube may comprise a second auxiliary electrode connected to theother main electrode.

The tube 1 is connected across terminals 71 and 8 of an A. C. supply of220 volts, 50 cycles per second through a choke 3. The tube 2 isconnected through a capacitor 4, a choke 5 and a part 6 of the choke 3.Both tube circuits further comprise a part 9192 of an auxiliary choke 9whose total number of turns 9193 is connected in parallel with theseries combination of tube 2, choke 5 and with the capacitor 4 to thesupply 71-8.

In this case, the auxiliary choke 9 consequently constitutes atransformer with the part 92-93 acting as a primary winding and thepart'91--93 as a secondary winding.

When applying the invention only in part by connecting the terminal 71of the supply to that end 91 of the auxiliary choke 9 which is connectedto the choke 3, in-

stead of connecting it to the tapping point 92, the arrangement wouldoperate as follows:

Upon connecting the arrangement to the supply, a current passing throughthe capacitor 4 and the auxiliary choke 9 produces a voltage ofapproximately 270 volts across said auxiliary choke and hence alsoacross the tube 2. At this voltage the tube 2 strikes and attains thearcdischarge condition within a small fraction of a second. Thephase-leading discharge current passing through the part 6 of the choke3 sets up a voltage of approximately 255 volts across the tube 1, thatis, a voltage in excess of the supply voltage of 220 volts of thearrangement,

whereupon this tube also attains the arc-discharge condition nearly atonce. During normal operation, the inductively stabilized tube 1 takes acurrent of approximately 420 milliamperes at an operating voltage ofapproximately volts, while the capacitatively stabilized tube 2 takes acurrent of approximately 440 milliamperes at an operating voltage ofabout 110 volts. It is to be noted that each tube consumes approximately40 watts; the slightly higher discharge current of the tube 2 resultingfrom the occurrence of higher harmonics in the capacitative circuit ofthis tube.

Should the tube 2 fail to ignite, no phase-leading current will passthrough the part 6 of choke 3, so that only the supply voltage having anominal value of 220 volts is set up across the tube 1 for ignition. Itis not certain whether the tube 1 will ignite under such conditions, butif it does ignite, it will take a current much smaller than 420milliamperes, since the reaction of the capacitative current branch oftube 2 is failing. If, however, the tube 1 becomes out of order, thetube 2 takes a current greatly exceeding 440 milliamperes, since thereaction of the inductive current branch of tube 1 is failing.

Said disadvantages are mitigated, or even substantially eliminated,according to the other feature of the invention, since the auxiliaryinductance 9 constitutes the volt- In the that the terminal 71 ofthesupplyisinot connectedtotpoint 91 but to point 92 of the auxiliaryinductance 9. Y

It will be evident that,.as a result of this, the voltage set up acrosstube 1 will exceed 220 volts if tube 2.is out of order and that, in thisevent, the tube 1 will take :more currentthan it would withoutthevoltage-increasing efliect of the auxiliary inductance9. 1

The. connection of. the terminal .71 to point 92 also results, in casethe tube 1 is defective, in the tube ,2 taking less current than if theterminal 71 is: connected to point 91. This will be readily appreciatedwhenconsidering that the tube 2 does nottakecurrentif the terminal 71 isconnected to point93 :of the auxiliary inductance 9, and that said tubetakes a maximum current with the terminal71 connected to point 91. Ifthe terminal 71 is connected to an intermediate point,.for examplepoint92, the current taken is smaller'than the. maximum value and exceedszero.

In one particular case, the 'number of secondary turns was 2485, thenumber of primary turns was 220.0,,thatis, 88% of the number ofsecondary turns. Through the part 92-93 of the auxiliary choke '9 andthecapacitor 4 of 5.5 microfarads passed a .no-load current of 67milliamperes; a no-load voltage of approximately .266 volts being setupacross tube 2 and a no-load voltage of approximately 250 volts being setup :across tube .1. During operation of tube 2, a no-load voltage ofapproximately 262 volts was set up across the tube 1, a no-load voltageof approximately 25.6 volts beingset up across tube,2 during operationoftube 1.

During normal operation, .a current of approximately 32 milliamperesflowed through the part 92-93, approximately 460 milliamperes flowedthrough the part 91-92, approximately. 440 milliamperes flowed throughtube 2, approximately 420 rnilliamperes flowed through tube 1,approximately 485 milliamlperes flowed through the capacitor 4, avoltage of approximately 1194 volts was set up across the part 91-93 ofthe auxiliary choke 9, a voltage of approximately 185 volts was set upacross the choke 3, the overall current-taken was approximately 470milliamperes and the power factor was approximately 0.95.

Each. of. said tube currents remained substantially independent of the.fact whether the other .tube was in or out of operation. In this case,the coil 3. had 1580 turns I The choke 5 was rated for 100 volts, 0.44ampere and consequently had an impedance of approximately 230 ohms. 1

While the invention has been described by means of a specific exampleand in a specific embodiment, I do not Wish to be limited thereto, forobvious modifications will occur to those skilled in the art withoutdeparting from t the spirit and scope of the invention.

What is claimed is:

l. Acircuit-arrangement for operating two low-pressure arc-dischargetubes without a starting switch, each of said tubes comprising twoactivated main electrodes .and at least one auxiliary electrode disposedwithin the discharge space on the wall of the discharge vessel andconnected electrically within the discharge space to one of said mainelectrodes and electrically insulated from the other of said mainelectrodes and extending parallel 'to the discharge .path of said tube,and each tube furtherand its part 6 had .3 turns, that is, approximately25% 5 of the total number of turns.

more having arare-gas fillingat a pressure of a few millimeters, saidcircuit-arrangementcomprising a first series circuit including a firstinductance and one of said two tubes, an alternating voltage source, asecond series circuit'including a second inductance, a capacitor havingan impedance exceeding that of said second inductance at the frequencyof the voltage of said source, and the other of said twotubes, saidsecond series circuit being connected between an intermediate point onsaid first inductance and one terminal of said voltage source, aconnection from said one terminal ofsaid voltage source to the end oftheone of said tubes .remote from said first inductance, and a transformerhaving a primary Winding connected in series with said capacitor acrosssaid voltage source and a voltage increasing secondary winding connectedbetween the end of said first inductance remote from said one tube .andthe terminal of said capacitor remote .from said .one terminal.

2. A circuit-arrangement as set forth in claim 1, whereinsaid primarywinding has 82 .to percent of the number of turnsof that ofsaidsecondary winding.

3. A circuit-arrangement as set forth in claim 2, wherein said firstinductance has 20 to 30 percent of its total number of turns disposedbetween said remote end and intermediate point of said first inductance.

References Cited in the file of this patent UNITED STATES PATENTS2,301,671 .Abadie Nov. 10, 1942 2,314,311 Karash Mar. 16, 1943 2,462,336Ruff Feb. 22, 1949

